What does 0.21 mean in ag/ab 4th generation test result mean? cut off value stated in the test 1.0 non reactive. does 0.21 mean a small portion of antigen or antibody was found or is it related to the reagents added? test was conducted after 6weeks?

That's a common misconception, but the answer is no: The low number does not mean a weakly positive test. Any number below the 1.0 cut-off is totally negative. For example there is no difference between say 0.1, 0.2, 0.5, and 0.9: all totally negative. The same blood sample tested 10 times often can give 10 different numbers. Your negative result is 100% proof you did not catch HIV when exposed.